// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/strings/sys_string_conversions.h"

#include <stddef.h>
#include <wchar.h>

#include "base/strings/string_piece.h"
#include "base/strings/utf_string_conversions.h"
#include "build/build_config.h"

namespace base {

std::string SysWideToUTF8(const std::wstring& wide)
{
    // In theory this should be using the system-provided conversion rather
    // than our ICU, but this will do for now.
    return WideToUTF8(wide);
}
std::wstring SysUTF8ToWide(const StringPiece& utf8)
{
    // In theory this should be using the system-provided conversion rather
    // than our ICU, but this will do for now.
    std::wstring out;
    UTF8ToWide(utf8.data(), utf8.size(), &out);
    return out;
}

#if defined(SYSTEM_NATIVE_UTF8) || defined(OS_ANDROID)
// TODO(port): Consider reverting the OS_ANDROID when we have wcrtomb()
// support and a better understanding of what calls these routines.

std::string SysWideToNativeMB(const std::wstring& wide)
{
    return WideToUTF8(wide);
}

std::wstring SysNativeMBToWide(const StringPiece& native_mb)
{
    return SysUTF8ToWide(native_mb);
}

#else

std::string SysWideToNativeMB(const std::wstring& wide)
{
    mbstate_t ps;

    // Calculate the number of multi-byte characters.  We walk through the string
    // without writing the output, counting the number of multi-byte characters.
    size_t num_out_chars = 0;
    memset(&ps, 0, sizeof(ps));
    for (size_t i = 0; i < wide.size(); ++i) {
        const wchar_t src = wide[i];
        // Use a temp buffer since calling wcrtomb with an output of NULL does not
        // calculate the output length.
        char buf[16];
        // Skip NULLs to avoid wcrtomb's special handling of them.
        size_t res = src ? wcrtomb(buf, src, &ps) : 0;
        switch (res) {
        // Handle any errors and return an empty string.
        case static_cast<size_t>(-1):
            return std::string();
            break;
        case 0:
            // We hit an embedded null byte, keep going.
            ++num_out_chars;
            break;
        default:
            num_out_chars += res;
            break;
        }
    }

    if (num_out_chars == 0)
        return std::string();

    std::string out;
    out.resize(num_out_chars);

    // We walk the input string again, with |i| tracking the index of the
    // wide input, and |j| tracking the multi-byte output.
    memset(&ps, 0, sizeof(ps));
    for (size_t i = 0, j = 0; i < wide.size(); ++i) {
        const wchar_t src = wide[i];
        // We don't want wcrtomb to do its funkiness for embedded NULLs.
        size_t res = src ? wcrtomb(&out[j], src, &ps) : 0;
        switch (res) {
        // Handle any errors and return an empty string.
        case static_cast<size_t>(-1):
            return std::string();
            break;
        case 0:
            // We hit an embedded null byte, keep going.
            ++j; // Output is already zeroed.
            break;
        default:
            j += res;
            break;
        }
    }

    return out;
}

std::wstring SysNativeMBToWide(const StringPiece& native_mb)
{
    mbstate_t ps;

    // Calculate the number of wide characters.  We walk through the string
    // without writing the output, counting the number of wide characters.
    size_t num_out_chars = 0;
    memset(&ps, 0, sizeof(ps));
    for (size_t i = 0; i < native_mb.size();) {
        const char* src = native_mb.data() + i;
        size_t res = mbrtowc(NULL, src, native_mb.size() - i, &ps);
        switch (res) {
        // Handle any errors and return an empty string.
        case static_cast<size_t>(-2):
        case static_cast<size_t>(-1):
            return std::wstring();
            break;
        case 0:
            // We hit an embedded null byte, keep going.
            i += 1; // Fall through.
        default:
            i += res;
            ++num_out_chars;
            break;
        }
    }

    if (num_out_chars == 0)
        return std::wstring();

    std::wstring out;
    out.resize(num_out_chars);

    memset(&ps, 0, sizeof(ps)); // Clear the shift state.
    // We walk the input string again, with |i| tracking the index of the
    // multi-byte input, and |j| tracking the wide output.
    for (size_t i = 0, j = 0; i < native_mb.size(); ++j) {
        const char* src = native_mb.data() + i;
        wchar_t* dst = &out[j];
        size_t res = mbrtowc(dst, src, native_mb.size() - i, &ps);
        switch (res) {
        // Handle any errors and return an empty string.
        case static_cast<size_t>(-2):
        case static_cast<size_t>(-1):
            return std::wstring();
            break;
        case 0:
            i += 1; // Skip null byte.
            break;
        default:
            i += res;
            break;
        }
    }

    return out;
}

#endif // OS_CHROMEOS

} // namespace base
